Oligosaccharides from Vitis vinifera grape seeds: a focus on gentianose as a novel bioactive compound

Abstract

AIM: Grape seeds (Vitis vinifera) are among the main constituents of grape pomace, also exploited in ingredients for nutraceutics and cosmeceutics, particularly regarding the phenolic fraction. The macromolecules of grape/wine include polyphenols, proteins and polysaccharides. Polysaccharides have been comprehensively studied because of their importance (technological and sensory properties in wines). Unlike polysaccharides, oligosaccharides have only recently been characterised. Following a concise focus about the polysaccharide composition of grape seeds, in this work we describes the purification and the identification of low molecular weight saccharides contained in the aqueous extract of grape seeds.

METHODS: A sequential two-step purification by size exclusion chromatography was carried out to fractionate compounds according to molecular weights. Chemical characterization of the combined fractions was performed by Magnetic Resonance Spectroscopy analysis and by high-resolution accurate-mass (Orbitrap mass analyzer).

RESULTS: Apart from sucrose and glucose, a fraction containing primarily a trisaccharide has been detected. Acetylation allowed the purification of the trisaccharide by flash chromatography. Structural determination on the acetylated derivative revealed the trisaccharide gentianose, a predominant carbohydrate reserve in storage roots of perennial Gentiana lutea, poorly discovered in other genera.

CONCLUSIONS:

The identification of gentianose, in grape seeds, could open new studies related to its biological functions, as well as to confirm its potential as prebiotic compound, as suggested by preliminary works.